1. Field of the Invention
The present invention relates to a sealing member for use in monolithic type catalytic exhaust gas purifiers and to a catalytic exhaust gas purifier provided with such a sealing member. More specifically, the invention relates to a sealing member made of heat-insulating resilient material for use in a monolithic type catalytic exhaust gas purifier and to a monolithic type catalytic exhaust gas purifier having such a sealing member.
2. Prior Art
In the conventional monolithic type catalytic exhaust gas purifier containing a monolithic catalyst in a casing, a woven fabric of metal, or a heat-insulating material such as ceramic fiber, or the like for supporting and sealing the catalyst is inserted into a space defined by an inner wall of the casing and the outer periphery of the monolithic catalyst.
Generally, exhaust gas purifiers in automobiles operate under severe conditions, being subjected at elevated temperature to vibrations of both the automobile bodies and the engines themselves. Consequently, when ceramic fibers are employed in a supporting and sealing member, appropriate selection of the bulk density thereof largely influences the durabiity of the ceramic fiber sealing member. In the case of a flattened cylinder-shaped monolithic type catalytic purifier, the heat expansion rate of the casing in the direction of the larger cross dimension differs from that in the direction of the smaller cross dimension. Specifically, the heat expansion rate in the smaller cross dimension of the casing is far greater than that in the larger cross dimension. This makes it difficult to provide a supporting and sealing ceramic fiber member with an appropriate bulk density. As a result, destruction of the supporting and sealing member, exhaust gas leakage, etc. are caused principally by inappropriate selection of the bulk density of the member.
The present invention provides a solution to the above-mentioned problem.